This application claims priority to an application entitled xe2x80x9cData Communication Apparatus and Method in a Multi-Carrier CDMA Communication Systemxe2x80x9d filed in the Korean Industrial Property Office on Nov. 10, 1999 and assigned Serial No. 99-49801, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a channel communication apparatus and method in a CDMA (Code Division Multiple Access) mobile communication system, and in particular, to a frequency assigning method for voice and data services and a channel transmitting and receiving apparatus and method using the same.
2. Description of the Related Art
The IS-95 CDMA communication system uses a single carrier, whereas the IMT-2000 CDMA communication system can provide multi-carrier service. The latter can provide spreading rates three times, six times, nine times, twelve times or higher than those in the former. A spreading rate based on the IS-95 standards will be referred to as xe2x80x9cspreading rate 1xe2x80x9d and a spreading rate three times higher than spreading rate 1 be xe2x80x9cspreading rate 3xe2x80x9d, etc.
A conventional spreading rate 1 system uses a frequency band of 1.25 MHz for voice and data services. FIG. 1 illustrates the 1.25-MHz frequency band and a single carrier in the spreading rate 1 system. The 1.25-MHz frequency band is called a xe2x80x9cFrequency Assignment (FA)xe2x80x9d.
The spreading rate 1 system transmits voice, data, and control signals associated with the voice and data transmission at the same time using the single FA. This is possible because orthogonal codes provide channelization for transmission of the voice, data; and control signals. As to the orthogonal code channels, voice is transmitted on a fundamental channel (FCH), data on a supplemental channel (SCH), and a control signal on a dedicated control channel (DCCH) or a common control channel (CCCH) depending on use of the control signal. The CCCH was a main control channel and a plurality of control channels may exist in reality. As shown in FIG. 1, the spreading rate 1 system orthogonally spreads a plurality of orthogonal code channel signals including the FCH, SCH, DCCH, and CCCH to one FA.
FIGS. 2 and 3 are respective block diagrams of a transmitting device and a receiving device in the spreading rate 1 system. The following description is conducted on the assumption that the channel transmitting and receiving device transmits and receives FCH, SCH, DCCH, and CCCH.
Referring to FIG. 2, each of channel transmitters 111, 113, 115, and 117 is comprised of an encoder, a symbol rate matcher, an interleaver, and an orthogonal spreader. Each orthogonal spreader generates an orthogonal code assigned to identify a corresponding channel. Thus, the channel transmitters 111, 113, 115, and 117 encode input signals, spread coded signals with their respective orthogonal codes, and transmit the transmission signals on their corresponding-channels. An adder 119 sums the output signals of the channel transmitters 111, 113, 115, and 117 and a complex spreader.121 complex-spreads the summed channel signals with a PN code. A low pass filter (LPF) 123 passes the PN-spread signal in the 1.25-MHz frequency band, and a modulator 127 transmits the output signal of the LPF 123 over a carrier signal received from an oscillator 125 (frequency upconversion).
Referring to FIG. 3, a demodulator 152 removes a carrier signal from an input signal (frequency downconversion) and an LPF 155 passes a signal in the 1.25-MHz frequency band from the demodulated signal. A complex despreader 157 despreads the output signal of the LPF 155 with a PN code by multiplying them and feeds the despread signal to channel receivers 161, 163, 165, and 167. Each channel receiver is comprised of an orthogonal despreader, a deinterleaver, and a decoder. Each orthogonal despreader generates an orthogonal code assigned to a corresponding channel. Thus, the channel receivers 161, 163, 165, and 167 despread the complex-despread signals with corresponding orthogonal codes and decode the orthogonally despread signals.
In operation, the channel transmitters 111, 113, 115, and 117 subject FCH, SCH, DCCH, and CCCH signals to encoding, interleaving, and orthogonal spreading. The adder 119 sums the orthogonally spread channel signals and the LPF 123 passes only a 1.25-MHz frequency band signal from the sum signal. The modulator 127 modulates the output signal of the LPF 123 using the carrier signal of the FA received from the oscillator 125 by multiplying the signals. The radio signal is converted to a baseband signal in the demodulator 153 and the LPF 155 in the receiving device. The demodulator 153 utilizes the oscillator 151 for generating the carrier of the corresponding FA like the modulator 127 in the transmitting device shown in FIG. 2. The baseband signal is orthogonally despread, divided into corresponding channel signals, deinterleaved, and channel-decoded in the channel receivers 161, 163, 165, and 167.
On the other hand, the spreading rate 3 system uses three FAs for voice and data services. That is, FCH, SCH, DCCH, and CCCH transmitters spread channel signals to three separate 1.25-MHz FAs in a multi-carrier scheme. This three FA structure for the spreading rate 3 system is illustrated in FIG. 4.
One third of each of the FCH, SCH, DCCH, and CCCH is present in each one FA in FIG. 4. FIGS. 5 and 6 are respective block diagrams of a transmitting device and a receiving device in the spreading rate 3 system.
Referring to FIG. 5, each of channel encoders 211, 213, 215, and 217 is comprised of an encoder, a symbol rate matcher, and an interleaver, for encoding corresponding input channel signals. Demultiplexers (DEMUXs) 221, 223, 225, and 227 dermultiplex the outputs of their corresponding channel encoders 211, 213, 215, and 217 and distribute the demultiplexed signals to the three FAs. Since the spreading rate 3 system uses three FAs, each of the DEMUXs 221, 223, 225, and 227 demultiplexes its corresponding channel encoder output into three signals. Four orthogonal-spreaders (231, 233, 235, 237; 241, 243, 245, 247, 249; and 251, 253, 255, 257, 259) are provided for each FA to identify four channels transmitted from four channel transmitters within the FA. Therefore, a total of 12 orthogonal spreaders are required for the three FAs. One complex spreader is needed for each FA and thus three complex spreaders 261, 263, and 265 are provided for the three FAs. LPFs 271, 273, and 275 low-pass filter the output signals of the complex spreaders 261, 263, and 265. Modulators 282, 294, and 286 are provided with oscillators 281, 283, and 285 for generating carrier frequency signals in the FAs and generate multi-carrier transmit signals.
Referring to FIG. 6, the receiving device is so configured that a receiving operation is performed in the reverse order of the transmitting operation in the transmitting device shown in FIG. 5. Demodulators 312, 314, and 317 demodulate the signals of corresponding FAs from an input multi-carrier signal using carrier frequencies related with the corresponding FAs generated from oscillators 311, 313, and 315. LPFs 321, 323, and 325 output baseband signals in the corresponding FAs. Complex despreaders 331, 333, and 335 and orthogonal despreaders (341, 343, 345, 347; 351, 353, 355, 357; and 361, 363, 365, 367) subject the baseband signals to complex depreading and orthogonal despreading. MUXs 371, 373, 375, and 377 each selectively receive a portion of the orthogonally despread signals and multiplex them. For example, the MUX 371 receives FCH signals from among the three-FA orthogonal despread signals, multiplexes them, and feeds the multiplexed signal to an FCH decoder 381.
Referring to FIGS. 5 and 6, in operation, FCH, SCH, DCCH, and CCCH signals are processed in the channel decoders 211, 213, 215, and 217. Each of the DEMUXs 221, 223, 225, and 227 demultiplexes an input channel signal to three signals in the three FAs. The demultiplexed signals are subject to orthogonal spreading in the orthogonal spreaders (231-239; 241-249; 251-259) and complex spreading in the complex spreaders 261, 263, and 265. The orthogonally spread signals are converted to radio signals while passing through the LPFs 271, 273, and 275 and the demodulators 282, 284, and 286. The radio signals are added up in the adder 290 and transmitted through an antenna. The multi-carrier radio signal is converted to baseband signals through the demodulators 312, 314, and 316 and the LPFs 321, 323, and 325 corresponding to the three FAs in the receiving device. The baseband signals are complex-PN despread in the complex despreaders 331, 333, and 335 and orthogonally despread in the orthogonal despreaders 341 to 367. The MUXs 371, 373, 375, and 377 respectively receive the orthogonally despread FCH, SCH, DCCH, and CCCH signals in the three FAs and multiplex them.
FIG. 7 illustrates a frequency assignment scheme in which voice and data are transmitted in different FAs. FIGS. 8 and 9 are respective block diagrams of a transmitting device and a receiving device according to the frequency assignment scheme.
Referring to FIGS. 7, 8, and 9, inter-frequency handoff happens when voice transmission transits to data transmission. The transmitting device and the receiving device performs the voice transmission/reception in the same manner as the FCH transmitter/receiver or the SCH transmitter/receiver in the spreading 1 system. The inter-frequency handoff is a process of switching a modulator 425 and a demodulator 457 to oscillators corresponding to an intended FA. Switches 423 and 455, controlled by an inter-frequency handoff command received from a higher layer, switch oscillators 419 and 451, respectively, corresponding to the FA for voice and oscillators 421 and 453, respectively, corresponding to the FA for data to the modulator 425 and demodulator 457, respectively.
In case voice transmission is to be switched to data transmission in the conventional system of transmitting voice and data in different FAs, the inter-frequency handoff is required, thereby increasing control complexity. Furthermore, channel transmitters and channel receivers must be provided with a plurality of oscillators to implement the inter-frequency handoff.
In addition, all of the carriers in a conventional spreading rate 3 system of CDMA 2000 communication system have the same characteristics between each of the carries transmits identical data and channels. However, each of the channel for CDMA 2000 communication system has different characteristics, as follows.
FCH (Fundamental Channel): It is constructed to be suitable for providing a voice service which has a lower transmission rate and enables a careful power control to provide a uniform service at all times.
SCH (Supplemental Channel): It is constructed to be suitable for packet service which required high transmission rate without being affected by transmission delays and allows the transmission of large amount of data through transmission rate control. Thus, more effective control can be gained by transmitting each of the channels on a different carrier based on the characteristics of each channel in the CDMA 2000 communication system.
It is, therefore, an object of the present invention to provide a frequency assigning apparatus and method for facilitating switching between voice transmission and data transmission in a multi-carrier CDMA communication system.
It is also an object of the present invention to provide a channel communication apparatus and method for facilitating switching between voice transmission and data transmission in a multi-carrier CDMA communication system.
It is another object of the present invention to provide a channel communication apparatus and method for changing the FA of a voice channel and control channels in current use to a specific FA and separately assigning a data channel to each FA if data transmission is requested in a multi-carrier CDMA communication system.
It is a further object of the present invention to provide a channel communication apparatus and method for assigning dedicated channels and common channels except for a dedicated data channel (i.e., a channel dedicated to only transmitting data signals; e.g., supplemental channel (SCH)) to a specific FA and separately assigning the dedicated data channel to each of the FAs in a multi-carrier CDMA communication system.
It is still another object of the present invention to provide a channel communication apparatus and method for distributing dedicated channels except for a dedicated data channel to all FAs and assigning a common channel to a specific FA if the dedicated data channel is not requested, and changing the FAs of the dedicated channels except for the dedicated data channel to a specific FA and separately assigning the dedicated data channel to each of the FAs if the dedicated data channel is requested in a multi-carrier CDMA communication system.
It is yet another object of the present invention to provide a channel communication apparatus and method for assigning dedicated channels except for a dedicated data channel to a specific FA and a common channel to a different FA if the dedicated data channel is not requested, and separately assigning the dedicated data channel to each of the FAs if the dedicated data channel is requested in a multi-carrier CDMA communication system.
It is a still further object of the present invention to provide a channel communication apparatus and method for distributing dedicated channels except for a dedicated data channel to all FAs and assigning a common channel to a specific FA if the dedicated data channel is not requested. If the dedicated data channel is requested, the dedicated channels except for the common channel are assigned to a specific FA different from the FA assigned to the common channel, and the dedicated data channel is separately assigned to each of the FAs.
The above objects can be achieved by providing a data communication apparatus and method in a multi-carrier CDMA communication system. A transmitting device determines whether a supplemental channel is transmitted. If the supplemental channel is transmitted, the transmitting device assigns the supplemental channel to each of those FAs having different carrier frequency bands and assigns the other channels (including a fundamental channel, a dedicated control channel, and a common control channel) to one of the FAs. A receiving device determines whether the supplemental channel exists in input channel signals. If the supplemental channel exists, the receiving device despreads supplemental channel signals in each of the FAs, connects the despread supplemental channel signals to a supplemental channel encoder, despreads the other channels in one of the FAs, and connects the other channel signals to corresponding channel decoders.